Biometrics is the science and technology of authentication (i.e. establishing the identity of an individual) by measuring the person's physiological or behavioral features. The term is derived from the Greek words “bios” for life and “metron” for degree.
In information technology, biometrics usually refers to technologies for measuring and analyzing human physiological characteristics such as fingerprints, eye retinas and irises, voice patterns, facial patterns, and hand measurements; especially for authentication purposes.
In a typical biometric system, a person registers with the system when one or more of their physiological characteristics are obtained, processed by a numerical algorithm, and entered into a database. Ideally, when the person logs into the system at a later time all of their features match. If someone else tries to log in as the same person, their biometric information does not fully match, so the system will not allow them to log in.
Performance of a biometric system is usually referred to in terms of the false accept rate (FAR), the false non-match or reject rate (FRR), and the failure to enroll rate (FTE or FER). In real-world biometric systems the FAR and FRR can typically be traded off against each other by changing parameters. One of the most common measures of real-world biometric systems is the rate at the setting at which both accept and reject errors are equal: the equal error rate (EER), also known as the cross-over error rate (CER). The lower the EER or CER, the more accurate the system is considered to be. Current technologies have widely varying Equal Error Rates (EER) from as low as 60% to as high as 99.9%.
Among all the biometric techniques, fingerprint-based identification is one of the oldest and most accurate methods which has been successfully used in numerous applications. Everyone is known to have unique, immutable fingerprints. A fingerprint is made of a series of ridges and furrows on the surface of the finger. The uniqueness of a fingerprint can be determined by the pattern of ridges and furrows as well as the minutiae points. Minutiae points are local ridge characteristics that occur at either a ridge bifurcation or a ridge ending. To implement fingerprint-based identification, an image or imprint of the fingerprint has to be acquired.
Similarly, an image of any uniquely identifiable skin surface can be used for identification. In addition to a single fingerprint, multiple fingertip images can be used for this purpose. In addition, images of the palm or the entire hand can be used as biometric identifiers.
In each of these identifying methods, a scanning process is used to acquire data representing a person's skin pattern characteristics. This allows the recognition of a person through quantifiable physiological characteristics that verify the identity of an individual. Optical methods are often used to obtain a visual image of the surface data of interest. In the case of fingerprint identification, a common optical data capture method includes placing one or more fingertips on a translucent platen. Beneath the platen, light reflected from the fingertips is directed through an optical path to an imaging device that captures image data.
Fingerprint scanners are available with image sensors that capture an image of a fingerprint. A signal representative of the captured image is then used for further processing. For example, the data may be used for one-to-one or one-to-many fingerprint matching. Many fingerprint scanners use a wedge-shaped prism in the optical path of the scanner. For example, U.S. Pat. No. 6,178,255, commonly owned with the present application, discloses a fingerprint scanner that uses a prism element to selectively collect roll prints or single or multiple-finger flat prints.
However, the inventor has found that traditional use of total internal reflection in a standard wedge shaped prism to capture a fingerprint or any other image results in foreshortening of the desired image. There is a need for an improved prism design to capture fingerprints that overcomes foreshortening effects.